1. Field of the Invention
The present invention relates to an inkjet printer and a controlling method thereof, the inkjet printer comprising a recording head for jetting ink from a plurality of jet openings, a sensor for examining jetting failure with respect to each jet opening of the recording head, and a sucking mechanism for sucking ink from each jet opening of the recording head.
2. Description of Related Art
An inkjet printer which forms an image on recording medium by jetting ink toward the recording medium from each jet opening provided in a recording head has been in practical use. Since an inkjet printer records an image by jetting ink from each jet opening of a recording head, among a plurality of jet openings, there are normal jet openings which normally jet ink and jetting openings which do not jet ink due to jetting failure. There are roughly two reasons which cause jetting failure. The first reason is generation of air bubble within a channel which is a passage to the jet opening. The second reason is clogging of ink at a jet opening where ink existing within the channel which is a passage to the jet opening gets more viscous or solidified when the recording head is left unused for a long period.
In order to recover from jetting failure of ink, an inkjet printer comprises a cleaning mechanism for cleaning the recording head. The cleaning mechanism is used to eliminate ink adhering around each jet opening by contacting a cap member to the recording head, sucking the ink from each jet opening of the recording head while making a sucking pump generate a sucking force to the cap member, and wiping the recording head with a wiper blade after the sucking.
In order to deal with the above-mentioned situation where the recording head is left unused for a long period, what is developed is one in which when a predetermined period passes since a certain timing, a cleaning mechanism automatically functions for performing the sucking of ink and the wiping of recording head (for example, see JP-Tokukai-2002-79693A).
Further, what is also developed is one in which a examining unit examines whether each of jet opening of the recording head is in a jetting failure state, prior to the sucking of ink and the wiping of recording head by the cleaning mechanism (for example, see JP-Tokukai-2002-79693A and JP-Tokukaihei-3-244546A). In the inkjet printer disclosed in the JP-Tokukai-2002-79693A, simulated jetting which jets ink without involving image recording is performed with respect to each jet opening in the recording head, and the examining unit examines whether there is ink jetting with respect to each jet opening and if the recording head has a jet opening causing jetting failure according to the examination result, the cleaning mechanism sucks ink and wipes the recording head, and on the contrary, if the recording head has no jet opening causing jetting failure, the cleaning head does not suck ink or wipe the recording head.
In the inkjet printer disclosed in JP-Tokukaihei-3-244546A, the examining unit examines whether there is ink jetting with respect to each jet opening and if the recording head has no jet opening causing jetting failure according to the examination result, image recording is performed without making the cleaning mechanism suck ink nor wipe the recording head. On the contrary, if the recording head has a jet opening causing jetting failure according to the examination result, the inkjet printer repeats the sucking of ink and the wiping of recording head by the cleaning mechanism until the examining unit detects no jet opening causing jetting failure.
However, even after the sucking of ink and the wiping of recording head are performed, there is a possibility of existence of a jet opening causing jetting failure. In particular, there is a case where a jet opening which is capable of jetting ink normally before the sucking of ink and the wiping of recording starts causing jetting failure after the sucking of ink and the wiping of recording head.
Further, as another method to recover from jetting failure of ink, there is a method to forcibly suck ink from each jet opening of the recording head. One example of such method is disclosed in JP-Tokukaihei-5-293968A. The method of JP-Tokukaihei-5-293968A makes the recording head perform the simulated jetting, measures temperature inside of the recording head at three moments which are: before the simulated jetting; right after the simulated jetting; and after predetermined period has passes since the simulated jetting, judges whether there is jetting failure according to a temperature variation among these three moments, and performs a process to recover from the jetting failure of the recording head by sucking ink from each jet opening of the recording head if it is judged that there is jetting failure.
However, with the method of JP-Tokukaihei-5-293968, ink is sucked always with a constant sucking force regardless of whatever cause of jetting failure (even if a cause of jetting failure is generation of air bubble or clogging of foreign material). Therefore, a recovering process corresponding to a cause of jetting failure is not performed, whereby there is inconvenience in conjunction with the recovering process. In other words, if a cause of jetting failure is generation of air bubble, it is possible to eliminate the air bubble with a comparatively low sucking force. However, in the case of sucking ink always at a certain sucking force more than the sucking force necessary for eliminating air bubble, ink which is not necessary for eliminating air bubble (ink which can be used for image recording) is to be uneconomically sucked, whereby it is ink wasting. On the other hand, if a cause of jetting failure is clogging of foreign material, it is necessary to have a comparatively high sucking force. If ink is sucked with a certain sucking force which is less than the sucking force necessary for eliminating foreign material, it is not possible to eliminate the foreign material.